1. Field of the Invention
This invention is related to the field of graphical information processing, more particularly, to image dithering.
2. Description of the Related Art
Part of the operation of many computer systems, including portable digital devices such as mobile phones, notebook computers and the like is the use of some type of display device, such as a liquid crystal display (LCD), to display images, video information/streams, and data. Accordingly, these systems typically incorporate functionality for generating images and data, including video information, which are subsequently output to the display device. Such devices typically include video graphics circuitry to process images and video information for subsequent display.
In digital imaging, the smallest item of information in an image is called a “picture element”, more generally referred to as a “pixel”. For convenience, pixels are generally arranged in a regular two-dimensional grid. By using this arrangement, many common operations can be implemented by uniformly applying the same operation to each pixel independently. Since each pixel is an elemental part of a digital image, a greater number of pixels can provide a more accurate representation of the digital image. The intensity of each pixel can vary, and in color systems each pixel has typically three or four components such as red, green, blue, and black.
Most images and video information displayed on display devices such as LCD screens are interpreted as a succession of image frames, or frames for short. While generally a frame is one of the many still images that make up a complete moving picture or video stream, a frame can also be interpreted more broadly as simply a still image displayed on a digital (discrete, or progressive scan) display. A frame typically consists of a specified number of pixels according to the resolution of the image/video frame. Information associated with a frame typically consists of color values for every pixel to be displayed on the screen. Color values are commonly stored in 1-bit monochrome, 4-bit palletized, 8-bit palletized, 16-bit high color and 24-bit true color formats. An additional alpha channel is oftentimes used to retain information about pixel transparency. The color values can represent information corresponding to any one of a number of color spaces.
Under certain circumstances, the total number of colors that a given system is able to generate or manage within the given color space—in which graphics processing takes place—may be limited. In such cases, a technique called dithering is used to create the illusion of color depth in the images that have a limited color palette. In a dithered image, colors that are not available are approximated by a diffusion of colored pixels from within the available colors. Dithering in image and video processing is also used to prevent large-scale patterns, including stepwise rendering of smooth gradations in brightness or hue in the image/video frames, by intentionally applying a form of noise to randomize quantization error. Dithering techniques are continually modified and improved to meet the increasing demand for ever-more reliable image fidelity even under conditions when practical limits are placed on the color and/or image resolution.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.